In order to enhance structural rigidity of gas turbine diffusers, it is common to find them incorporated with struts or spokes. The struts, typically numbering between three and six, can be either equally spaced circumferentially or non-uniformly distributed around the diffuser annulus at certain axial (or meridional) location. FIG. 1 shows a meridional view of a typical annular diffuser 100 with a strut 102. The strut 102 is an un-cambered airfoil-shaped structure, with a straight leading edge 104 and straight trailing edge 106 perpendicular to an inner diffuser wall 108 and an outer diffuser wall 110. The inner wall 108 and the outer wall 110 define a diffuser annulus 111 of the diffuser 100.
Apart from providing structural support, struts themselves offer no aerodynamic benefit to the diffuser as they create a blockage, depending on their number and thickness, by locally reducing the passage area, which in turn leads to local loss of pressure recovery around the location of the struts and a reduced thermal efficiency.
U.S. 2004/0228726 A1 discloses an exhaust diffuser with struts having their middle portions shifted toward donwstream side, compared with their hub-side and tip-side portions.
EP 1 731 734 A2 discloses a turbofan engine with a high pressure turbine, a low pressure turbine and an annular transition duct therebetween. The duct includes fairings having leading edges extending radially between platforms between which is defined an inlet flow area E for each flow passage.
U.S. Pat. No. 5,338,155 discloses a multi-zone diffuser for a turbo-machine. The diffuser is bound by a hub-end, inner part and an outer part which are connected by a plurality of welded streamlined struts which are fundamentally conical with s/t=constant, where s is the strut chord length and t is the strut pitch.
DE 10 2008 060 847 A1 relates to a turbo-engine with a high-pressure turbine and a low pressure turbine with a flow channel therebetween, the flow channel comprising struts. The leading edge of the struts is inclined in meridian direction.
EP 0 833 060 A2 relates to a blade for an axial fluid machine. The blade is formed to a profile in such a manner that it advances toward a main stream along a stagger line connecting a blade leading edge to a blade trailing edge.
In view of the above-described situation, there exists a need for an improved technique that enables to provide structural support to a gas turbine diffuser, while substantially avoiding or at least reducing one or more of the above-identified problems.